The question of whether to run before or after lifting weights is common for those combining resistance training and cardiovascular exercise in a single session. Running focuses on cardiovascular endurance, while lifting weights targets muscular strength, power, and size. Because the body has limited energy reserves, the order in which these activities are performed directly influences the specific physiological results you can expect. The optimal sequence depends entirely on which fitness outcome you prioritize.
Why Lifting Should Come First
Lifting weights should be performed first in a combined session to maximize gains in strength and muscle size. High-intensity resistance training relies on immediate energy systems, such as the adenosine triphosphate and phosphocreatine (ATP-PCr) system and the glycolytic system. These systems require a readily available supply of intramuscular glycogen to fuel the powerful bursts of effort needed for heavy lifts.
Starting with running, especially a moderate-to-high-intensity effort, depletes these glycogen stores and compromises the energy needed for lifting. The nervous system must also be fresh to recruit the maximum number of muscle fibers required for a high-quality set. When the nervous system is rested, it effectively signals muscles for maximal force production, which stimulates strength and muscle growth.
The goal of resistance training is to provide sufficient mechanical overload to stimulate protein synthesis pathways in the muscle. This process, governed by the mammalian target of rapamycin (mTOR) signaling pathway, is best activated when the muscle can handle a heavy workload. Placing the lifting session first ensures that fatigue has not yet reduced the amount of weight you can lift or the number of repetitions you can perform.
How Running Before Lifting Affects Performance
Performing a substantial run before lifting weights acutely reduces performance in the subsequent resistance training session. The preceding endurance work causes muscular fatigue, leading to a temporary decrease in the muscle’s ability to contract and generate force.
This acute fatigue directly impairs the quality of your lifting, making it difficult to maintain proper form and reducing power output. A decrease in power output, especially in explosive movements, means the stimulus for fast-twitch muscle fiber recruitment is blunted. When stabilizing muscles, such as those around the core and joints, are tired from running, the risk of technical breakdown during complex lifts like squats or deadlifts increases.
The “interference effect” describes a potential molecular conflict between the two types of exercise adaptations. Endurance training activates the signaling pathway known as 5′ adenosine monophosphate-activated protein kinase (AMPK), which regulates metabolic processes. AMPK activation following endurance exercise can temporarily inhibit the mTOR pathway, which is responsible for protein synthesis and muscle growth.
Adjusting the Sequence Based on Fitness Goals
The sequence is determined by your primary fitness goal; always perform the most important activity when you are freshest. If improving endurance is your main objective, starting with your run is the correct choice. Prioritizing the run guarantees that your cardiovascular system and running mechanics are not hindered by muscular fatigue from lifting.
If your goal is general health maintenance or improving both strength and endurance simultaneously, maximize the recovery time between the two activities. A separation of at least six hours between resistance training and endurance sessions minimizes the potential for interference. This allows the body’s energy systems and signaling pathways to recover and focus on the specific adaptations of each mode.
A final consideration is using low-intensity running as a dynamic warm-up before lifting. A short, five to ten-minute jog at a low intensity is acceptable, as it raises the heart rate and increases blood flow without causing significant fatigue or depleting energy stores. This light cardio primes the body for the resistance work to come, but it should not be confused with a moderate or high-intensity training run.